RAPT2MQTT

Configuration

MQTT Host

MQTT Port

MQTT Username

MQTT Password

RAPT Email

RAPT API Secret

Poll Interval (seconds)

Notification MQTT Topic

Auto-start on container launch

Gravity Display

Hide product links (I already have my gear)

Bridge

Console

Dashboard

Select devices to monitor. Values refresh automatically.

Charts

Device

Metric

Range

Axis

Active Brews

Brew History

No previous brews.

Start a New Brew

Beer Name

Original Gravity (OG)

Target Beer Temp (°C)

Temperature Sensor don't have one?

Temperature Controller don't have one?

Feedback Temp Source

Notes

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Active

Devices & Configuration

Hydrometer

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Controller

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Temp Source

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Beer Target

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Beer Temp

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Fridge Temp

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Specific Gravity

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ABV

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OG

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Fridge Target

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Fermentation

-- ABV

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Beer Temperature

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Specific Gravity

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Fridge Controller

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Fermentation Chart

Metric

Range

Removes physically impossible spikes (e.g. a -20°C TILT reading or a sudden SG jump from sloshing). Filters any change faster than 2°C/min for temperature or 0.002 SG/min. Turn off to see raw unfiltered data.

Smart Temperature Feedback

Controller Mode

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Beer Error

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Last Adjustment

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Next Check

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How does this work?

The problem: Your temperature controller has a probe sitting in the fridge air. When you set it to 17.5°C, it heats or cools until the air reaches 17.5°C and then stops. But beer has far more thermal mass than air — 20 litres of liquid changes temperature much slower than the air around it. The controller thinks it's done while your beer is still degrees off target. It can take days to naturally equilibriate.

The solution: Your hydrometer (e.g. TILT) is floating inside the beer. It knows the actual liquid temperature. We use that as the source of truth and adjust the controller's target to compensate for the difference.

The maths: Every 5 minutes, we calculate:

Error = your beer target − actual beer temp (from hydrometer)
Adjustment = error × 1.5 (gain)
New controller target = your beer target + adjustment

So if your beer target is 17.5°C and the hydrometer reads 19.2°C, the error is −1.7°C. Multiply by 1.5 gain = −2.55°C adjustment. The controller target gets set to 15.0°C — deliberately overshooting cold to pull the liquid down faster. As the beer approaches 17.5°C, the error shrinks, the overshoot shrinks, and the controller target converges back to 17.5°C. We also clamp to safe bounds (0–35°C) and only send an update if the change exceeds 0.3°C (deadband), to avoid hammering the RAPT API with micro-adjustments.

Why the overshoot matters — the hysteresis deadzone: Your controller has a hysteresis setting (e.g. cooling hysteresis of 0.5°C). This means the compressor won't kick in until the air temperature rises above the target by that amount. If we set the controller target to exactly your beer target (17.5°C), and the fridge air is already sitting at 17.4°C, the compressor will never fire — the air is within hysteresis, so the controller thinks everything is fine, even though the liquid is still 19°C. By overshooting the target lower (e.g. 15.0°C), we ensure the air temperature is far enough above the controller's target to actually trigger a cooling cycle. The gain multiplier is what creates this overshoot — the bigger the error, the further we push past target to guarantee the hardware acts.

Why not learn a calibration constant? A static offset between fridge air and beer liquid would be simpler, but it doesn't work in practice. The relationship changes constantly — it depends on fermentation activity (yeast generate heat), ambient temperature, how full the fridge is, the volume and surface area of the fermenter, whether the door was opened, and even the beer's specific gravity. A calibration constant learned from one brew would be wrong for the next, and wrong within the same brew as conditions change. Instead, we measure the actual error right now and correct for it every 5 minutes. This is standard proportional servo control — the same approach used in industrial process control, HVAC systems, and PID loops everywhere. We just skip the I (integral) and D (derivative) terms because the 5-minute sample rate and the controller's own hardware delays (compressor cooldown, hysteresis) make them more likely to cause oscillation than help.

Your controller's own limits still apply. If it has a compressor cooldown of 5 minutes, it physically cannot start a new cooling cycle faster than that. If it has a heating hysteresis of 0.3°C, it won't kick in until the air drifts that far below target. We can't override these — they're hardware safety limits set in the RAPT Portal. What we can do is make sure the target the controller is chasing actually reflects where the beer needs to be, not just where the air is.

Reminders & Notifications

When

Day

Message

Icon

Recipe

Upload recipe photo

Brew Log

Legendary Brews

Your completed brews, rated and documented for posterity. Every great beer deserves a story.

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Current Temperature

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Target Temperature

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Specific Gravity

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Mode

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Device Info

Name	--
Device Type	--
Use	--
MAC Address	--
Firmware	--
Signal	--
Temp Unit	--
Sensor	--
Telemetry Frequency	--
Last Activity	--
Manage	--

Runtime Stats

Total Runtime	--
Cooling Runtime	--
Cooling Starts	--
Heating Runtime	--
Heating Starts	--

Controller Settings

Cooling Allowed	--
Heating Allowed	--
PID Enabled	--
Cooling Hysteresis	--
Heating Hysteresis	--
Compressor Delay	--
Mode Switch Delay	--
High Temp Alarm	--
Low Temp Alarm	--
Bluetooth	--

Metric

Range

Axis

Signal Strength

Target Temperature

Change the target temperature on the RAPT controller via cloud API.

Target Temperature (°C)

PID Control

Toggle PID mode and tune parameters. Changes are sent to the RAPT API.

PID is currently: --

Proportional (P)

Integral (I)

Derivative (D)

Device Management

All devices that have ever connected to RAPT2MQTT. Customize names, add photos, or forget devices you no longer use.

About RAPT2MQTT

Version ...

RAPT2MQTT is an open-source bridge between Kegland RAPT brewing devices and MQTT, built for homebrewers who want real control over their fermentation.

This project was born from frustration with cloud-only brewery management. Your data should live on your network, in your Home Assistant, under your control.

What You Get -- Free

RAPT Temperature Controller

Full cloud API integration -- monitor temperature, target, mode (heating/cooling/idle), PID tuning, all from your own dashboard.

Multi-TILT Hydrometer Support

Live specific gravity and beer temperature from TILT hydrometers via MQTT. Multiple TILTs, multiple brews, no problem.

HACS / Home Assistant Sensors

Every metric published to MQTT is ready for Home Assistant auto-discovery. Temperature, SG, ABV, mode -- all as native sensors.

Custom MQTT Notifications

Brew reminders, SG stability alerts, and day-based triggers -- all pushed to your MQTT broker for Home Assistant automations.

Smart Temperature Feedback

Cascaded control that uses the hydrometer (in-liquid) temperature to adjust the fridge controller target. Nail your beer temp, not your air temp.

Brew Session Tracking

Multi-brew management with fermentation charts, OG/FG/ABV tracking, brew logs, needle gauge, and full event history.

Built By a Homebrewer

This isn't a corporate product. It's one person, one fridge, one hydrometer, writing code between brew days. Every feature exists because I needed it for my own fermentation.

If you want an integration for gear I don't own -- I need to buy it, brew with it, understand it, and then write the code. That's where the community funding comes in.

Currently Supported

These devices work right now, out of the box.

Controller Supported

RAPT Temperature Controller

Full cloud API integration. Monitor fridge and target temperature, set target remotely, detect heating/cooling/idle mode, compressor delay, hysteresis settings, PID tuning, signal strength.

Get one: kegland.com.au

Full support

Sensor Supported

TILT Hydrometer

Live specific gravity and beer temperature via TiltPi MQTT. All TILT colours supported. Multiple TILTs, multiple concurrent brews.

Get one: tilthydrometer.com

Full support (via TiltPi)

Bridge Supported

Home Assistant / MQTT

All device metrics published to MQTT. Native Home Assistant sensors via auto-discovery. Brew reminders and alerts as MQTT notifications with MDI icons.

Full support

Controller Sensor Supported

Smart Temperature Feedback

Cascaded control loop that reads the hydrometer temperature (in the liquid) and adjusts the controller's fridge target to hold your actual beer at the desired temperature.

Built in

Request an Integration

I don't own every piece of brewing gear on the market. To write an integration properly, I need to:

Buy the device -- hardware costs money
Brew with it -- understand how it actually works in a real fermentation
Reverse-engineer the API -- figure out the data format, protocols, and quirks
Write the integration -- and give it away to the community for free

If you want to see a specific device supported, fund it below. Once funded, it goes to the top of the build queue.

Sensor

iSpindel

DIY digital hydrometer. WiFi-based, open hardware. Needs MQTT integration + calibration support.

Get one: ispindel.de

$0 / $45

Sensor

Plaato Airlock

CO2 activity-based fermentation monitor. Cloud API with activity data, temperature, and estimated ABV.

Get one: plaato.io

$0 / $120

Controller Sensor

Grainfather Connect

All-in-one electric brewery with Bluetooth/WiFi. Brew-day automation, mash profiles, and fermentation tracking.

Get one: grainfather.com

$0 / $350

Controller

BrewZilla / Robobrew

Kegland all-in-one brew system. Gen 4 has Bluetooth + app control. Needs protocol analysis.

Get one: kegland.com.au

$0 / $280

Controller

Inkbird ITC-308 WiFi

Budget temperature controller. WiFi model has cloud API. Popular entry-level fermentation control.

Get one: inkbird.com

$0 / $40

Sensor

Tilt Pro

Higher-resolution TILT with extended range. Same BLE protocol, finer SG resolution (4 decimal places).

Get one: tilthydrometer.com

$0 / $130

Sensor

RAPT Pill

Kegland's floating hydrometer. BLE-based, cloud API via RAPT Portal. Direct competitor to TILT.

Get one: kegland.com.au

$0 / $55

Suggest a Device

Don't see your gear? Let me know what you're brewing with and I'll look into it.

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Support the Project

RAPT2MQTT is free, open source, and built by one person. Every feature you use was written between brew days, tested on real fermentations, and given away to the community.

I don't own all the brewing gear. To build integrations for new devices, I need to buy them, brew with them, understand them, and then write the code. Your support makes that possible.

What Your Support Funds

Hardware

Buying the actual brewing devices to reverse-engineer and integrate.

Ingredients

Every integration needs real brew days to test. Grain, hops, yeast, and time.

Development

Ongoing development, bug fixes, and new features for the whole community.

Buy Me a Beer

Choose a support tier or enter a custom amount.

A Pint

$5

Cheers! Keeps the lights on.

A Six Pack

$15

Funds a brew day's worth of testing.

A Keg

$50

Covers a budget device integration.

The Full Brew

$100+

Directly funds a new device purchase.

Community Fund

$0

raised so far

Payment integration coming soon. For now, reach out on GitHub to sponsor.

Already Free

These features are available right now, at no cost:

RAPT Temperature Controller integration (cloud API)
Multi-TILT hydrometer support via MQTT
Home Assistant / HACS sensor auto-discovery
Custom MQTT notifications and brew reminders
Smart temperature feedback (hydrometer-driven cascaded control)
Multi-brew session management with charts and logs
Dark-theme web UI -- no frameworks, no bloat

RAPT2MQTT

Bridge between RAPT (Kegland) brewing devices and MQTT for Home Assistant and other home automation platforms.

Getting Started

Go to Config and enter your MQTT broker address and port.
Enter your RAPT email and API Secret.
Set the Poll Interval (default 300s).
Click Save Configuration, then Start the bridge.
Devices appear in the sidebar as they are discovered.

MQTT Topics

RAPT Data	`RAPT/temperatureController`
RAPT Commands	`RAPT/temperatureController/Command`
TILT Data (inbound)	`TiltPi`
Notifications (outbound)	`RAPT2MQTT/notify` (configurable)

TILT Hydrometer Integration

RAPT2MQTT displays live TILT data if it publishes to your MQTT broker on the TiltPi topic.

TiltPi + Custom MQTT Node

Open TiltPi Node-RED at http://tiltpi.local:1880
Find the ui_template node for your TILT color
Add a function node, then rbe, then mqtt out to topic TiltPi

Alternative: TiltBridge (ESP32)

Flash TiltBridge firmware onto an ESP32 for native MQTT output.

Brew Reminders & Notifications

Set reminders on active brews (e.g. "Dry hop on day 5"). When triggered, a notification is published to your configured MQTT topic. Set up a Home Assistant automation to pick up RAPT2MQTT/notify messages and send push notifications.

Links

GitHub	MetalOctopus/RAPT-to-MQTT
RAPT Portal	app.rapt.io
RAPT API Docs	api.rapt.io/index.html

Configuration

Bridge

Console

Dashboard

Charts

Active Brews

Brew History

Start a New Brew

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Devices & Configuration change

Fermentation

Beer Temperature

Specific Gravity

Fridge Controller

Fermentation Chart

Smart Temperature Feedback

Reminders & Notifications

Recipe

Brew Log

Legendary Brews

Edit Brew Notes

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Temperature (24h)

Specific Gravity (24h)

Device Info

Runtime Stats

Controller Settings

Signal Strength

Target Temperature

PID Control

Device Management

Edit Device

About RAPT2MQTT

What You Get -- Free

Built By a Homebrewer

Currently Supported

RAPT Temperature Controller

TILT Hydrometer

Home Assistant / MQTT

Smart Temperature Feedback

Request an Integration

iSpindel

Plaato Airlock

Grainfather Connect

BrewZilla / Robobrew

Inkbird ITC-308 WiFi

Tilt Pro

RAPT Pill

Suggest a Device

Support the Project

What Your Support Funds

Buy Me a Beer

Community Fund

Already Free

RAPT2MQTT

Getting Started

MQTT Topics

TILT Hydrometer Integration

TiltPi + Custom MQTT Node

Alternative: TiltBridge (ESP32)

Brew Reminders & Notifications

Links

Devices & Configuration